1. Field of the Invention
This invention relates to a switch network comprising N inputs and T outputs for mutually and individually connecting any P (P.ltoreq.N and P.ltoreq.T) inputs chosen from the N inputs and any P outputs chosen from the T outputs.
By varying on the positions of the switches in the switch network it is possible to alter the choice of the P inputs or the P outputs that are mutually and individually connected.
This rearrangement must be done causing a minimum of disturbance, i.e., by making the smallest possible number of changes to existing individual connections.
Of course, the terms inputs and outputs as employed above are interchangeable from the point of view of the switch network, which means that only the relation T&gt;N need be maintained.
2. Description of the Prior Art
Switching networks are installed for example in telecommunication satellites to establish P simultaneous communication channels to be chosen by the operator from N possible resources and to connect the channels individually to P out of T pieces of equipment of the same type to be associated with these resources.
They are used for example, to overcome failures of these pieces of equipment (to a maximum of T-P). As a rule, two symmetrical networks in which the switches are operated simultaneously are used on either side of the pieces of equipment.
This arrangement enables each of the P (out of N) inputs to be connected to one of the P (out of T) pieces of equipment, and enables this equipment then to be connected by the symmetrical network to one input out of T of this symmetrical network which will lead to an output having the same position as the input of the first network.
The switches used in these networks have four poles and are capable of connecting a first pole to a second, a third or a fourth and, correspondingly, connecting the third pole to the fourth, first or second poles. With no restrictions as to the assignment of numbers to poles more precisely, there are in the prior art:
a three-position switch capable of connecting a first pole to a second and a third to a fourth, or a first pole to a third and a second to a fourth, or a first pole to a fourth and a second to a third; and PA1 a four-position switch capable of connecting a first pole to a second and a third to a fourth, a first to a third, a first to a fourth and a second to a third, or finally in the last position a second to a fourth.
Different structures of such switch networks are disclosed in U.S. Pat. No. 5,469,001. In these structures, the essential aim is to minimize the number of switches, because of their weight and their cost. The implementation of these structures is specific to each application. This produces a form of network consisting of inputs, outputs, switches and links. These links are in the form of voluminous, solid waveguides. Links that are too long must be provided with flexible waveguide sections to absorb expansion. Thus, the physical layout of the network is defined by locating its component switches and waveguides in a network structure. The most constraining feature in this respect is the routing of the waveguides as they are voluminous and their curvatures must be limited, which makes it desirable to achieve as straight a path as possible for each waveguide, an objective that is impeded by the fact that an installed waveguide hinders the routing of other waveguides that must cross it, the crossings requiring changes of height. This necessitates an expensive layout design procedure leading to complex routings and entails a high cost in the manufacture of the waveguides resulting in, generally, a switch network of relatively high cost and weight.
The same drawbacks are found in links constructed using other technologies (notably coaxial or microstrip lines).
The aim of this invention is to overcome all these drawbacks by providing a switch network that has a simple layout and that can benefit extensively from earlier implementations, in which the links between switches are all straight and short, and that can be constructed as modules.